It is commonly believed that the combination of antidepressant medications (ADM) and psychotherapy is more efficacious in the treatment of depression than either treatment alone. There is evidence that adding cognitive therapy (CT) enhances the initial effects of ADM, but most of the relevant studies have suffered from low power. Findings from numerous studies also suggest that CT has an enduring effect, but most of the evidence has been relevant to the prevention of relapse - the return of symptoms associated with the treated episode. There is little evidence on the more critical prevention question: whether prior exposure to CT prevents recurrence - the onset of new episodes. What is needed is a study with power sufficient to detect the benefits that might accompany the addition of CT to ADM, and that can address the attendant cost-effectiveness questions. Over the last few years we have randomized 450 depressed outpatients (150 at each of three sites) to ADM alone or to ADM plus CT. All patients are treated to remission and then to recovery (allowing up to 18 months in each phase) with up to four different classes of antidepressant medications plus augmentation, as clinically indicated. A random half of the patients receive CT in addition to medications. Recovered patients are then assigned randomly to either maintenance medications or medication withdrawal;patients in the combined condition are withdrawn from ongoing CT. Patients are then followed for a three-year period for the purpose of detecting recurrences. The main hypotheses are that: (1) rates of remission and recovery will be higher in the combined treatment relative to ADM alone;and (2) prior exposure to CT will protect against recurrence following medication withdrawal. At this point, intake is complete, and 450 patients have been randomized to treatment. Estimated rates of remission (75% of all assigned) and recovery (83% of those who reach remission) have been strong, and over 150 recovered patients have entered the maintenance phase to date. Completion of this trial will allow for powerful tests of treatment effects with respect to remission, recovery, and recurrence, as well as the exploration of underlying mechanisms (mediation) and the delineation of patient-type by treatment interactions (moderation) that can be used to refine treatment guidelines.